Many techniques have been developed to modify photographic images in various ways. For instance, well known techniques have been developed to enhance the edges of images, crop the images, change the contrast of images, alter the colors in the images, and so forth. While these techniques may improve the quality of the images in various respects, these techniques do not make substantial changes to the overall style of the images. In other words, the techniques do not produce a significant transformation from one basic motif of creative presentation to another.
On the other hand, a human artist routinely does achieve such creative transformation when producing an artwork. Namely, the artist may paint or draw a picture based on an original scene in a manner that is based on the creative and abstract judgment of the artist. Thus, the objects in the picture are generally not easily predictable transformations of the shapes and colors in the original scene.
For instance, an artist may choose to produce a simplified or perhaps cartoon-like transformation of an original scene. This style is used in many different forms of art, such as posters, water color paintings, graphics design, advertising art, cartoons, animation, and so forth. In this style, the artist typically simplifies the shapes and colors in the original scene in a manner which reflects high-level artistic judgment. For instance, the artist may modify a complex original scene by reducing it to a smaller number of relatively simple shapes having solid colors. The artist may select the colors in the picture to produce a pleasing effect to the eye.
The field of non-photorealistic rendering (NPR) attempts to automatically transform the content of images in non-routine and sometimes abstract ways, as would, for example, a human artist. However, automating the human judgment of an artist has proven to be a very challenging task. For instance, one technique has been described which transforms an image into a line drawing with bold edges and large regions of constant color. However, as appreciated by the present inventors, this technique is a rather indiscriminate transformation of the original image according to simple mapping protocols. The transformation does not take into account the complex judgment exercised by the artist and does not consider the global interplay among the different colors and shapes that appear in the picture.
Accordingly, there is an exemplary need in the art to produce an image-transformation technique that more accurately models the complex human judgment of an artist. There is also a need in the art to produce such an image-transformation technique that is efficient and relatively easy to use.